Clematis vitalba-sourced ‘’flavescence dorée’’ phytoplasmas and Wolbachia in naturally infected populations of Dictyophara europaea

Screening for “flavescence dorée”-related phytoplasmas (FD) sourced by Clematis vitalba as reservoir plant and Wolbachia infection in Dictyophara europaea populations was carried out in south eastern Europe and north Italy. Both FD and Wolbachia were characterized by multilocus sequence typing (MLST). All FD infected populations from Serbia and Italy share the identical Wolbachia strain wEur. Populations from Montenegro and Serbia differed by very high FD infection rate in the absence of Wolbachia (DewEur-) and low FD infection (ca. 3%) in the presence of Wolbachia (DewEur+), respectively. These populations did not differ in vectoring abilities and shared the most reported FD MLST genotype. Additionally, C. vitalba as FD source plants exhibited similarly high infection rate at both locations. All molecular diversity parameters of D. europaea populations were found to be lower in Serbia and Italy where DewEur+ populations are present. No evidence of direct fitness effects on D. europaea caused by Wolbachia infection was registered. Bacterial competition for limited resources in DewEur+ populations and an absence of competition in DewEur-populations, suggests that bacterial interactions have shaped the observed discrepancy in FD infection rates in the current source-plant pathosystem.